If...

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When you get your son innoculated, the doctor doesn't keep the baby. That, plus residual doubt.

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I just go along with the OPs hypothetical. "God asked" so there is no doubt. Now, "a voice claiming to be god" ..that'd be a different question.

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I personally find it hard to construct an interpretation of OP's hypothetical that removes all doubt. Note: I am not talking about an attack-on-inductive-reasoning "how do we really know the sun will rise tomorrow?" sort of doubt. Humans reason about and conceive of animate entities much differently than they do inanimate ones, and animate things are inherently "tricky."

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